1. Field of the Invention
The present invention pertains in general to oil field production and fluid handling equipment and in particular to the use of certain polymer liners in downhole production, disposal and injection tubulars.
2. Description of Related Art
Downhole tubulars are commonly used in conventional methods to produce oil from underground reservoirs including free flowing, reciprocating rod pumped, plunger lifted, gas lifted, submersible pumped, progressive cavity pumped, and hydraulically lifted methods. Other common uses include source, injection or disposal tubulars used to transport corrosive gases and fluids such as water and/or carbon dioxide (CO2) either for disposal or in secondary recovery operations.
Historically, wells produced using conventional reciprocating rod pumping units, rotating progressive cavity pumps, or plunger lift units in particular have evidenced problems with tubing and/or production equipment due to abrasion of the moving parts of the artificial lift devices (for example rods, rod couplings and plungers) on the tubing walls. These failures may be accelerated by the presence of corrosive elements and/or by the deviation of the well bore. The production tubing joints are protected with various corrosion resistant organic coatings that have been used in these applications to protect these areas from corrosive attack for many decades. A polyethylene liner greatly reduces these failures.
The lining of pipe and tubing with polymer liners for corrosion control and abrasion resistance has been practiced heretofore. For example, polyolefin liners have been installed in flow lines and fittings for the transportation of corrosive fluids in the chemical process industry for some time. The use of thermoplastic polymer liner materials such as polyethylene and polyvinylchloride is common in oil country tubular goods utilized primarily for water injection strings and disposal strings. Polyethylene has been used in downhole tubulars as shown in U.S. Pat. Re. 36,362, issued Nov. 2, 1999.
One objective of this invention is to utilize certain polyolefin liners for the purpose of eliminating metal to metal contact between the rods, rod couplings, or plunger and the production string in artificially lifted production wells, thereby reducing the frequency of failures to all of the mentioned components due to corrosion, friction, wear or a combination thereof. An additional benefit of the reduction in friction in these wells is an increased operating efficiency by reducing the power required to operate the wells and increasing the fall rates of the plungers.
Still another object of this invention is to provide protection of OCTG by providing an opportunity to reduce the operating costs by reducing the chemical treatment costs of the well fluids.
Yet another object of this invention is to increase the pressure rating of the tubing because the hoop strength is now a sum of that of the liner in addition to the pipe it is installed in. Unbreached, the liner will control internal corrosion of the tubing and allow for the use of lower than usual quality OCTG because no internal corrosion allowance is required.
A common problem with prior art plastic coating and liner materials is mechanical damage from installation practices or intrusive wellbore operations performed after the tubulars are placed in service. This is commonly referred to as “wireline damage” in the industry. Still another object of the present polyolefin liner system invention is to reduce the frequency of this type of damage.
As noted above, tubular goods, such as oil country tubular goods (“OCTG's”) (e.g., well casing, tubing, drillpipe, drill collars, and line pipe) and flowline tubular goods, are often used for transportation of gases, liquids, and mechanical equipment, including various applications related to extraction of petroleum and natural gas from underground reservoirs, transportation of petroleum, natural gas, and other materials, such as solution mining and slurry transport lines in the mining industry. OCTG's may be used to transport the product from the underground reservoir, and also to house mechanical equipment (e.g., artificial lift devices, rod couplings, plungers, reciprocating rod pumping units, rotating progressive cavity pumps, and plunger lift units), electrical equipment (e.g., well monitoring equipment), and/or transport gases or liquids for disposal operations or secondary removal operations. These gases and liquids may contain corrosive materials such as, by way of example only, salt water, dissolved oxygen, CO2, or H2S. In addition, flowline tubular goods may be used to transport petroleum, petroleum products, natural gas, or other gases or liquids from one point to another. The gases and liquids which flow within flowlines may, comprise corrosive and/or abrasive components. In addition, flowline tubular goods may also occasionally require the use of mechanical equipment, such as pigs, to clean or service the tubular good.
With respect to moving mechanical equipment and abrasive fluids, such as reciprocating or rotating rods or pumps or drilling or mining slurries (e.g., drilling mud), friction and abrasion may cause wear, fatigue, and even failure of the pipe and/or the equipment. In addition, this wear, fatigue, or failure may be accelerated due to the presence of corrosive or abrasive materials, such as, for example CO2, or by deviations in the direction of the well bore. As noted above, one method of combatting this wear in oil well production equipment is disclosed in U.S. Pat. No. RE36,362 to Jackson, incorporated herein by reference.
In addition to the possible acceleration of mechanical wear, fatigue, and failure, the presence of corrosive material, in and of itself, may cause chemical damage to the OCTG's and flowline tubular goods. By way of example only, the presence of CO2, when contacted with metal or other materials may cause corrosion, dusting, rusting, or pitting, which may lead to failure of the material. In addition, the presence of microbiological active agents, such as bacteria, may produce chemicals which influence or accelerate corrosion.
It would therefore be desirable to create tubular goods which decrease or eliminate the mechanical and/or chemical wear, fatigue, or failure caused by the conditions surrounding the extraction of materials such as petroleum or natural gas and transportation of materials, thereby potentially increasing the life and productivity of the tubular good.